BACKGROUND OF THE INVENTION
1. Field of the Invention [0001]
The present invention relates to an error correction method for correcting an error of composite coded data having at least one second symbol between first symbols forming first coded data which is error-correction-coded using a first error correction code, between synchronization data pieces for synchronizing data, or between the first symbol and the synchronization data, the second symbol forming second coded data which is error-correction-coded using a second error correction code having a lower degree of redundancy than the first error correction code. The present invention also relates to a reproduction apparatus for carrying out such an error correction method. [0002]
2. Description of the Related Art [0003]
Optical discs which are representative recording mediums have recently increased in density and capacity, and thus require improved reliability. Various error correction methods for correcting errors caused by defects of a recording medium itself or dust or scratches on the recording medium have been proposed (for example, U.S. Pat. No. 6,367,049B1, pages 5 to 6 and FIG. 5; and Japanese National-Phase PCT Laid-Open Publication No. 2001-515642, [0004] pages 10 to 11 and FIG. 2).
FIG. 2 shows an exemplary composite coded [0005] data piece 203, together with a first coded data piece 201 and a second coded data piece 202. With reference to FIG. 2, an error correction method will be described.
The composite coded [0006] data piece 203 includes first coded data pieces 206, 207, 208, 209, 210 and 211 which have been error-correction-coded using a first error correction code; and second coded data pieces 212, 213, 214, 215, 216, 217, 218 and 219 which have been error-correction-coded using a second error correction code having a lower degree of redundancy than the first error correction code. The composite coded data piece 203 also includes synchronization data pieces 204 and 205 for synchronizing the first coded data piece and the second coded data piece.
The first coded [0007] data piece 201 is error-corrected using 24 first error correction codes. The second coded data piece 202 is error-correction-coded using 304 second error correction codes. The first coded data piece 201 is divided into the plurality of first coded data pieces 206 through 211. The second coded data piece 202 is divided into the plurality of second coded data pieces 212 through 219. The first coded data pieces 206 through 211 each include a plurality of first symbols, and the second coded data pieces 212 through 219 each include a plurality of second symbols.
Between two adjacent synchronization data pieces, among a plurality of synchronization data pieces, at least one first coded data piece is provided. For example, as shown in FIG. 2, the first coded [0008] data pieces 206 through 208 including the first symbols are arranged between two adjacent synchronization data pieces 204 and 205. Thus, at least one first symbol is provided between two adjacent synchronization data pieces.
Between the synchronization data piece and the first coded data piece, at least one second coded data piece is provided. Between two adjacent first coded data pieces, at least one second coded data piece is provided. For example, as shown in FIG. 2, the second coded [0009] data piece 212 is provided between the synchronization data piece 204 and the first coded data piece 206. The second coded data piece 213 is provided between two adjacent first coded data pieces 206 and 207. Thus, at least one second symbol is provided between the synchronization data piece and the first symbol, and between two first symbols. In FIG. 2, 38 second symbols are arranged between two first symbols adjacent to each other in a recording direction 220. 38 second symbols are arranged between the synchronization data piece and the first symbol adjacent to each other in the recording direction 220.
The first coded [0010] data piece 201 and the second coded data piece 202 are respectively divided into the first coded data pieces 206 through 211 and the second coded data pieces 212 through 219 and thus arranged, such that local error areas on a recording medium are dispersed in the composite coded data piece 203. (Hereinafter, such a process of arranging the data in a dispersed manner will be referred to as “interleaving”.)
On the recording medium, the above-described composite coded [0011] data pieces 203 are arranged in the recording direction 220.
The first error correction code is a Reed Solomon code over an extension field obtained by adding root a of the primitive polynomial (expression 1) to a prime field GF(2), having 30 information bytes and 32 parity bytes. The second error correction code is a Reed Solomon code over an extension field obtained by adding root a of the primitive polynomial (expression 1) to a prime field GF(2), having 216 information bytes and 32 parity bytes. [0012]
x 8 +x 4 +x 3 +x 2+1=0 expression 1
FIG. 3 shows a [0013] flowchart 30 illustrating an error correction method of the composite corrected data piece 203.
In [0014] step 301, the first coded data piece 201 is error-corrected. At this point, the first coded data piece 201 is subjected to de-interleaving, which is the opposite transform to interleaving.
In [0015] step 302, erasure locator information, which indicates a position of erasure in the second coded data piece 202, is generated. The erasure locator information can be generated by, for example, one of the following three methods.
FIGS. 4 through 6 show the state of the synchronization data pieces or the first symbols when the second coded data piece is determined to represent erasure. In FIGS. 4 through 6, mark “X” represents that no synchronization data piece is detected or that the first symbol is incorrect. Mark “◯” represents that synchronization data is detected or that the first symbol is correct. FIGS. 4 through 6 show a portion of the data corresponding to one row (or a plurality of rows), in the recording direction, of the composite corrected [0016] data piece 203 which is arranged in rows and columns.
With reference to FIG. 4, method 1 will be described. When, as shown in FIG. 4, the detection states of both the [0017] synchronization data pieces 401 and 402 which are adjacent to each other along a recording direction 404 ( synchronization data pieces 401 and 402 maybe first symbols) are “X”, a second coded data piece 403 between the synchronization data pieces 401 and 402 is determined to represent erasure. Thus, erasure locator information representing such a determination result is generated.
With reference to FIG. 5, method 2 will be described. When, as shown in FIG. 5, the detection state of the [0018] synchronization data pieces 501, 502 and 503 which are consecutive in a recording direction 506 ( synchronization data pieces 501, 502 and 503 may be first symbols) is “X◯X”, the second coded data piece 504 between the synchronization data pieces 501 and 502, and the second coded data piece 505 between the synchronization data pieces 502 and 503, are determined to represent erasure. Thus, erasure locator information representing such a determination result is generated.
With reference to FIG. 6, method 3 will be described. When, as shown in FIG. 6, the detection states of three or more consecutive [0019] first symbols 602 through 604 between synchronization data pieces 601 and 605 which are adjacent in a recording direction 610 ( synchronization data 601 and 605 may be first symbols) are “X”, the second coded data pieces 606 through 609, including the second coded data piece 606 between the first symbol 602 and the synchronization data 601 (detection state: “◯”) and the second coded data piece 609 between the first symbol 604 and the synchronization data 605 (detection state: “◯”), are determined to represent erasure. Thus, erasure locator information representing such a determination result is generated.
In step [0020] 303 (FIG. 3), erasure locator information generated in step 302 is used to perform erasure error correction of the second coded data pieces in the range represented by expression 2.
ε+2ν≦32 expression 2
Here, ε is the number of erasure positions, and v is the number of errors other than erasure. [0021]
By the above-described methods for generating erasure locator information, a second coded data piece may become undesirably uncorrectable. FIG. 7 is a partial enlarged view of the composite encoded [0022] data piece 203, which shows an example of an error pattern by which the second coded data piece becomes uncorrectable.
[0023] Data pieces 701 through 703 are each a first coded data piece or a synchronization data piece. Data pieces 704 through 709 are partial data pieces of the second coded data piece provided in the vicinity of the data piece 702. At the positions of marks “◯” and “X”, one of a partial synchronization data piece, a first symbol or a second symbol is provided. In data pieces 701 through 703, mark “X” represents that no synchronization data is detected or that the first symbol is incorrect. Mark “◯” represents that synchronization data is detected or that the first symbol is correct. In data pieces 704 through 709, mark “X” represents that the second symbol which has been read is incorrect, and the other portions represent that the second symbol which has been read is correct.
It is assumed that the errors as shown in FIG. 7 occur. By the above-described methods for generating erasure locator information, the second symbols, which are incorrect, are not all determined to represent erasure. Since the second coded data is erasure-error-corrected in the range represented by expression 2, only up to 16 errors other than erasure can be corrected. Therefore, the errors of the pattern as shown in FIG. 7 cannot be corrected. [0024]
By the above-mentioned methods for generating erasure locator information, the state determination result of synchronization data piece which is used for generating the erasure locator information is either “detected” or “not detected”. When a synchronization data piece is detected with a positional offset, the symbols positioned before such a synchronization data piece are incorrect with a high probability, and the symbols positioned after such a synchronization data piece are correct with a high probability. The reason is that the offset of the synchronization is corrected by a reproduction apparatus, and the symbols positioned after the synchronization data piece detected with a positional offset is read after the offset of synchronization is corrected. [0025]
In the case where the state determination result of synchronization data piece is either “detected” or “not detected”, the following occurs. When a synchronization data piece detected with a positional offset is determined to be “detected”, the symbols positioned before such a synchronization data piece may not be determined to represent erasure, despite the fact that these symbols are incorrect. As a result, the incorrect symbols may not be corrected. When a synchronization data piece detected with a positional offset is determined to be “not detected”, even the correct symbols positioned after such a synchronization data piece may be determined to represent erasure. In such a case, the number of erasure positions is increased and the correction may become impossible. [0026]
SUMMARY OF THE INVENTION
According to one aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, and a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one of the plurality of second symbols is provided between two adjacent first symbols of the plurality of first symbols. The plurality of first symbols include an Nth first symbol, an (N+1)th first symbol and an (N+2)th first symbol, where N is an integer. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece and the second coded data piece; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the error location information indicates that no error is detected in the Nth first symbol and the (N+2)th first symbol and that an error is detected in the (N+1)th first symbol, determining at least one of the plurality of second symbols provided adjacent to the (N+1)th first symbol as representing erasure. [0027]
In one embodiment of the invention, the erasure locator information generation step further includes the step of, when the error location information indicates that no error is detected in the Nth first symbol and the (N+2)th first symbol and that an error is detected in the (N+1)th first symbol, determining at least one second symbol provided adjacent to the (N+1)th first symbol, among at least one second symbol provided between the Nth first symbol and the (N+1)th first symbol as representing erasure; and determining at least one second symbol provided adjacent to the (N+1)th first symbol, among at least one second symbol provided between the (N+1)th first symbol and the (N+2)th first symbol as representing erasure. [0028]
In one embodiment of the invention, the erasure locator information generation step further includes the step of, when the error location information indicates that an error is detected in both of two adjacent first symbols, determining all the second symbols provided between the two adjacent first symbols as representing erasure. [0029]
According to another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, and second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least two of the plurality of second symbols are provided between two adjacent first symbols of the plurality of first symbols. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece and the second coded data piece; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the error location information indicates that a first symbol detected to have no error and a first symbol detected to have an error are adjacent to each other, determining at least one second symbol provided adjacent to the first symbol detected to have an error, among at least two second symbols provided between the first symbol detected to have no error and the first symbol detected to have an error, as representing erasure: and determining at least one second symbol provided adjacent to the first symbol detected to have no error as not representing erasure. [0030]
In one embodiment of the invention, the erasure locator information generation step further includes the step of, when the error location information indicates that an error is detected in both of two adjacent first symbols, determining all the second symbols provided between the two adjacent first symbols as representing erasure. [0031]
According to still another aspect of the invention, a reproduction method for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. The plurality of synchronization data pieces include an Nth synchronization data piece, an (N+1)th synchronization data piece, and an (N+2)th synchronization data piece, where N is an integer. The reproduction method includes a reading step of reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result: an erasure locator information generation step of generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction step of performing erasure error correction of the coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the Nth synchronization data piece and the (N+2)th synchronization data piece are detected and the (N+1)th synchronization data piece is not detected, determining at least one of the plurality of symbols provided adjacent to the (N+1)th synchronization data piece as representing erasure. [0032]
In one embodiment of the invention, the erasure locator information generation step further includes the step of, when the synchronization detection information indicates that the Nth synchronization data piece and the (N+2)th synchronization data piece are detected and the (N+1)th synchronization data piece is not detected, determining at least one symbol provided adjacent to the (N+1)th synchronization data piece, among at least one symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure; and determining at least one symbol provided adjacent to the (N+1)th synchronization data piece, among at least one symbol provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece as representing erasure. [0033]
In one embodiment of the invention, the erasure locator information generation step further includes the step of, when the synchronization detection information indicates that neither of the two adjacent synchronization data pieces are detected, determining all the symbols provided between the two undetected synchronization data pieces as representing erasure. [0034]
According to still another aspect of the invention, a reproduction method for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least two of the plurality of symbols are provided between two adjacent synchronization data pieces of the plurality of synchronization data pieces. The reproduction method includes a reading step of reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction step of performing erasure error correction of the coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that a synchronization data piece adjacent to a detected synchronization data piece is not detected, determining at least one symbol adjacent to the undetected synchronization data piece, among at least two symbols provided between the detected synchronization data piece and the undetected synchronization data piece, as representing erasure; and determining at least one symbol provided adjacent to the detected synchronization data piece as not representing erasure. [0035]
In one embodiment of the invention, the erasure locator information generation step further includes the step of, when the synchronization detection information indicates that neither of the two adjacent synchronization data pieces are detected, determining all the symbols provided between the two undetected synchronization data pieces as representing erasure. [0036]
According to still another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that there is a synchronization data piece which is not detected and the error location information indicates that no error is detected in the first symbols immediately on both sides of the undetected synchronization data piece, determining at least one of the plurality of second symbols provided adjacent to the undetected synchronization data piece as representing erasure. [0037]
In one embodiment of the invention, at least two first symbols are provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one second symbol is provided between two adjacent first symbols among the at least two first symbols. The erasure locator information generation step further includes the step of, when the error location information indicates that there is a first symbol detected to have an error and at least one of the error location information and the synchronization detection information indicates that one of a detected synchronization data piece and a first symbol detected to have no error is immediately on each of both sides of the first symbol detected to have an error, determining at least one of the plurality of second symbols provided adjacent to the first symbol detected to have an error as representing erasure. [0038]
According to still another aspect of the invention, a reproduction method for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. The plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. The reproduction method includes a reading step of reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction step of performing erasure error correction of the coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0039]
In one embodiment of the invention, the plurality of synchronization data pieces include an (N+2)th synchronization data piece. The erasure locator information generation step further includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one symbol provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece as not representing erasure. [0040]
According to still another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one second symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0041]
In one embodiment of the invention, the plurality of synchronization data pieces include an (N+2)th synchronization data piece. The erasure locator information generation step further includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one second symbol provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece as not representing erasure. [0042]
According to still another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. A prescribed first symbol is provided between the Nth synchronization data piece and the (N+1)th synchronization data piece. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one second symbol provided between the prescribed first symbol and the (N+1)th synchronization data piece as representing erasure. [0043]
In one embodiment of the invention, the plurality of synchronization data pieces include an (N+2)th synchronization data piece. Another prescribed first symbol is provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece. The erasure locator information generation step further includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one second symbol provided between the (N+1)th synchronization data piece and the another prescribed first symbol as not representing erasure. [0044]
According to still another aspect of the invention, a reproduction method for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces of the plurality of synchronization data pieces. The reproduction method includes a reading step of reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction step of performing erasure error correction of the coded data piece based on the erasure locator information. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, determining at least one symbol provided between the consecutive synchronization data pieces as representing erasure. [0045]
According to still another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on the erasure locator information. The erasure locator information generation step of, when the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, determining at least one second symbol provided between the consecutive synchronization data pieces as representing erasure. [0046]
In one embodiment of the invention, the erasure locator information generation step further includes the step of determining at least one first symbol provided between the consecutive synchronization data pieces as representing erasure. [0047]
According to still another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, and a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one of the plurality of second symbols is provided between two adjacent first symbols of the plurality of first symbols. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece and the second coded data piece; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating at least first erasure locator information and second erasure locator information which represent an erasure position of the second coded data piece, based on the error location information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on at least one of the first erasure locator information and the second erasure locator information. The erasure error correction step includes the step of, when there is an error which cannot be corrected based on the first erasure locator information, performing erasure error correction of the second coded data piece based on the second erasure locator information. [0048]
In one embodiment of the invention, the erasure locator information generation step includes the steps of: when all the errors can be corrected based on the first erasure locator information, generating erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the first erasure locator information, and when all the errors can be corrected based on the second erasure locator information, generating erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the second erasure locator information. [0049]
In one embodiment of the invention, the plurality of first symbols include an Nth first symbol, an (N+1)th first symbol and an (N+2)th first symbol, where N is an integer. The erasure locator information generation step includes the step of, when the error location information indicates that no error is detected in the Nth first symbol and the (N+2)th first symbol and that an error is detected in the (N+1)th first symbol, determining at least one of the plurality of second symbols provided adjacent to the (N+1)th first symbol as representing erasure. [0050]
According to still another aspect of the invention, a reproduction method for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. The reproduction method includes a reading step of reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation step of generating at least first erasure locator information and second erasure locator information which represent an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction step of performing erasure error correction of the coded data piece based on at least one of the first erasure locator information and the second erasure locator information. The erasure error correction step includes the step of, when there is an error which cannot be corrected based on the first erasure locator information, performing erasure error correction of the coded data piece based on the second erasure locator information. [0051]
In one embodiment of the invention, the erasure locator information generation step includes the steps of when all the errors can be corrected based on the first erasure locator information, generating erasure locator information for erasure error correction of another coded data piece using an identical method as the method used for generating the first erasure locator information, and when all the errors can be corrected based on the second erasure locator information, generating erasure locator information for erasure error correction of another coded data piece using an identical method as the method used for generating the second erasure locator information. [0052]
In one embodiment of the invention, the plurality of synchronization data pieces include an Nth synchronization data piece, an (N+1)th synchronization data piece, and an (N+2)th synchronization data piece, where N is an integer. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the Nth synchronization data piece and the (N+2)th synchronization data piece are detected and the (N+1)th synchronization data piece is not detected, determining at least one of the plurality of symbols provided adjacent to the (N+1)th synchronization data piece as representing erasure. [0053]
In one embodiment of the invention, the plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0054]
In one embodiment of the invention, the erasure locator information generation step includes the step of, when the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, determining at least one symbol provided between the consecutive synchronization data pieces as representing erasure. [0055]
According to still another aspect of the invention, a reproduction method for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The reproduction method includes a reading step of reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation step of detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation step of performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation step of generating at least first erasure locator information and second erasure locator information which represent an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction step of performing erasure error correction of the second coded data piece based on at least one of the first erasure locator information and the second erasure locator information. The erasure error correction step includes the step of, when there is an error which cannot be corrected based on the first erasure locator information, performing erasure error correction of the second coded data piece based on the second erasure locator information. [0056]
In one embodiment of the invention, the erasure locator information generation step includes the steps of: when all the errors can be corrected based on the first erasure locator information, generating erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the first erasure locator information, and when all the errors can be corrected based on the second erasure locator information, generating erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the second erasure locator information. [0057]
In one embodiment of the invention, the erasure locator information generation step includes the steps of, when the synchronization detection information indicates that there is a synchronization data piece which is not detected and the error location information indicates that no error is detected in the first symbols immediately on both sides of the undetected synchronization data piece, determining at least one of the plurality of second symbols provided adjacent to the undetected synchronization data piece as representing erasure. [0058]
In one embodiment of the invention, at least two first symbols are provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one second symbol is provided between two adjacent first symbols among the at least two first symbols. The erasure locator information generation step includes the step of, when the error location information indicates that there is a first symbol detected to have an error and at least one of the error location information and the synchronization detection information indicates that one of a detected synchronization data piece and a first symbol detected to have no error is immediately on each of both sides of the first symbol detected to have an error, determining at least one of the plurality of second symbols provided adjacent to the first symbol detected to have an error as representing erasure. [0059]
In one embodiment of the invention, the plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. The erasure locator information generation step includes the step of, when the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, determining at least one second symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0060]
In one embodiment of the invention, the erasure locator information generation step includes the step of, when the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, determining at least one second symbol provided between the consecutive synchronization data pieces as representing erasure. [0061]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, and a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one of the plurality of second symbols is provided between two adjacent first symbols of the plurality of first symbols. The plurality of first symbols include an Nth first symbol, an (N+1)th first symbol and an (N+2)th first symbol, where N is an integer. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece and the second coded data piece; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on the erasure locator information. When the error location information indicates that no error is detected in the Nth first symbol and the (N+2)th first symbol and that an error is detected in the (N+1)th first symbol, the erasure locator information generation section determines at least one of the plurality of second symbols provided adjacent to the (N+1)th first symbol as representing erasure. [0062]
In one embodiment of the invention, when the error location information indicates that no error is detected in the Nth first symbol and the (N+2)th first symbol and that an error is detected in the (N+1)th first symbol, the erasure locator information generation section determines at least one second symbol provided adjacent to the (N+1)th first symbol, among at least one second symbol provided between the Nth first symbol and the (N+1)th first symbol as representing erasure; and determining at least one second symbol provided adjacent to the (N+1)th first symbol, among at least one second symbol provided between the (N+1)th first symbol and the (N+2)th first symbol as representing erasure. [0063]
In one embodiment of the invention, when the error location information indicates that an error is detected in both of two adjacent first symbols, the erasure locator information generation section determines all the second symbols provided between the two adjacent first symbols as representing erasure. [0064]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, and a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least two of the plurality of second symbols are provided between two adjacent first symbols of the plurality of first symbols. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece and the second coded data piece; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on the erasure locator information. When the error location information indicates that a first symbol detected to have no error and a first symbol detected to have an error are adjacent to each other, the erasure locator information generation section determines at least one second symbol provided adjacent to the first symbol detected to have an error, among at least two second symbols provided between the first symbol detected to have no error and the first symbol detected to have an error, as representing erasure; and determines at least one second symbol provided adjacent to the first symbol detected to have no error as not representing erasure. [0065]
In one embodiment of the invention, when the error location information indicates that an error is detected in both of two adjacent first symbols, the erasure locator information generation section determines all the second symbols provided between the two adjacent first symbols as representing erasure. [0066]
According to still another aspect of the invention, a reproduction apparatus for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. The plurality of synchronization data pieces include an Nth synchronization data piece, an (N+1)th synchronization data piece, and an (N+2)th synchronization data piece, where N is an integer. The reproduction apparatus includes a reading section for reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction section for performing erasure error correction of the coded data piece based on the erasure locator information. When the synchronization detection information indicates that the Nth synchronization data piece and the (N+2)th synchronization data piece are detected and the (N+1)th synchronization data piece is not detected, the erasure locator information generation section determines at least one of the plurality of symbols provided adjacent to the (N+1)th synchronization data piece as representing erasure. [0067]
In one embodiment of the invention, when the synchronization detection information indicates that the Nth synchronization data piece and the (N+2)th synchronization data piece are detected and the (N+1)th synchronization data piece is not detected, the erasure locator information generation section determines at least one symbol provided adjacent to the (N+1)th synchronization data piece, among at least one symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure; and determines at least one symbol provided adjacent to the (N+1)th synchronization data piece, among at least one symbol provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece as representing erasure. [0068]
In one embodiment of the invention, when the synchronization detection information indicates that neither of the two adjacent synchronization data pieces are detected, the erasure locator information generation section determines all the symbols provided between the two undetected synchronization data pieces as representing erasure. [0069]
According to still another aspect of the invention, a reproduction apparatus for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least two of the plurality of symbols are provided between two adjacent synchronization data pieces of the plurality of synchronization data pieces. The reproduction apparatus includes a reading section for reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result an erasure locator information generation section for generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction section for performing erasure error correction of the coded data piece based on the erasure locator information. When the synchronization detection information indicates that a synchronization data piece adjacent to a detected synchronization data piece is not detected, the erasure locator information generation section determines at least one symbol provided adjacent to the undetected synchronization data piece, among at least two symbols provided between the detected synchronization data piece and the undetected synchronization data piece, as representing erasure; and determines at least one symbol provided adjacent to the detected synchronization data piece as not representing erasure. [0070]
In one embodiment of the invention, when the synchronization detection information indicates that neither of the two adjacent synchronization data pieces are detected, the erasure locator information generation section determines all the symbols provided between the two undetected synchronization data pieces as representing erasure. [0071]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on the erasure locator information. When the synchronization detection information indicates that there is a synchronization data piece which is not detected and the error location information indicates that no error is detected in the first symbols immediately on both sides of the undetected synchronization data piece, the erasure locator information generation section determines at least one of the plurality of second symbols provided adjacent to the undetected synchronization data piece as representing erasure. [0072]
In one embodiment of the invention, at least two first symbols are provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one second symbol is provided between two adjacent first symbols among the at least two first symbols. When the error location information indicates that there is a first symbol detected to have an error and at least one of the error location information and the synchronization detection information indicates that one of a detected synchronization data piece and a first symbol detected to have no error is immediately on each of both sides of the first symbol detected to have an error, the erasure locator information generation section determines at least one of the plurality of second symbols provided adjacent to the first symbol detected to have an error as representing erasure. [0073]
According to still another aspect of the invention, a reproduction apparatus for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. The plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. The reproduction apparatus includes a reading section for reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction section for performing erasure error correction of the coded data piece based on the erasure locator information. When the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0074]
In one embodiment of the invention, the plurality of synchronization data pieces include an (N+2)th synchronization data piece. When the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one symbol provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece as not representing erasure. [0075]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on the erasure locator information. When the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one second symbol provided between the Nth synchronization data piece and the (N+1) th synchronization data piece as representing erasure. [0076]
In one embodiment of the invention, the plurality of synchronization data pieces include an (N+2)th synchronization data piece. When the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one second symbol provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece as not representing erasure. [0077]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. A prescribed first symbol is provided between the Nth synchronization data piece and the (N+1)th synchronization data piece. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on the erasure locator information. When the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one second symbol provided between the prescribed first symbol and the (N+1)th synchronization data piece as representing erasure. [0078]
In one embodiment of the invention, the plurality of synchronization data pieces include an (N+2)th synchronization data piece. Another prescribed first symbol is provided between the (N+1)th synchronization data piece and the (N+2)th synchronization data piece. When the synchronization detection information indicates that the (N+1)th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one second symbol provided between the (N+1) th synchronization data piece and the another prescribed first symbol as not representing erasure. [0079]
According to still another aspect of the invention, a reproduction apparatus for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces of the plurality of synchronization data pieces. The reproduction apparatus includes a reading section for reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction section for performing erasure error correction of the coded data piece based on the erasure locator information. When the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, the erasure locator information generation section determines at least one symbol provided between the consecutive synchronization data pieces as representing erasure. [0080]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating erasure locator information which represents an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on the erasure locator information. When the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, the erasure locator information generation section determines at least one second symbol provided between the consecutive synchronization data pieces as representing erasure. [0081]
In one embodiment of the invention, the erasure locator information generation section determines at least one first symbol provided between the consecutive synchronization data pieces as representing erasure. [0082]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, and a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one of the plurality of second symbols is provided between two adjacent first symbols of the plurality of first symbols. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece and the second coded data piece; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating at least first erasure locator information and second erasure locator information which represent an erasure position of the second coded data piece, based on the error location information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on at least one of the first erasure locator information and the second erasure locator information. When there is an error which cannot be corrected based on the first erasure locator information, the erasure error correction section performs erasure error correction of the second coded data piece based on the second erasure locator information. [0083]
In one embodiment of the invention, when all the errors can be corrected based on the first erasure locator information, the erasure locator information generation section generates erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the first erasure locator information. When all the errors can be corrected based on the second erasure locator information, the erasure locator information generation section generates erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the second erasure locator information. [0084]
In one embodiment of the invention, the plurality of first symbols include an Nth first symbol, an (N+1)th first symbol and an (N+2) the first symbol, where N is an integer. When the error location information indicates that no error is detected in the Nth first symbol and the (N+2)th first symbol and that an error is detected in the (N+1)th first symbol, the erasure locator information generation section determines at least one of the plurality of second symbols provided adjacent to the (N+1)th first symbol as representing erasure. [0085]
According to still another aspect of the invention, a reproduction apparatus for reproducing a coded data piece from a recording medium having a plurality of synchronization data pieces and the coded data piece which is error-correction-coded recorded thereon is provided. The coded data piece includes a plurality of symbols. At least one of the plurality of symbols is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. The reproduction apparatus includes a reading section for reading the plurality of synchronization data pieces and the coded data piece from the recording medium; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an erasure locator information generation section for generating at least first erasure locator information and second erasure locator information which represent an erasure position of the coded data piece, based on the synchronization detection information; and an erasure error correction section for performing erasure error correction of the coded data piece based on at least one of the first erasure locator information and the second erasure locator information. When there is an error which cannot be corrected based on the first erasure locator information, the erasure error correction section performs erasure error correction of the coded data piece based on the second erasure locator information. [0086]
In one embodiment of the invention, when all the errors can be corrected based on the first erasure locator information, the erasure locator information generation section generates erasure locator information for erasure error correction of another coded data piece using an identical method as the method used for generating the first erasure locator information. When all the errors can be corrected based on the second erasure locator information, the erasure locator information generation section generates erasure locator information for erasure error correction of another coded data piece using an identical method as the method used for generating the second erasure locator information. [0087]
In one embodiment of the invention, the plurality of synchronization data pieces include an Nth synchronization data piece, an (N+1)th synchronization data piece, and an (N+2)th synchronization data piece, where N is an integer. When the synchronization detection information indicates that the Nth synchronization data piece and the (N+2)th synchronization data piece are detected and the (N+1)th synchronization data piece is not detected, the erasure locator information generation section determines at least one of the plurality of symbols provided adjacent to the (N+1)th synchronization data piece as representing erasure. [0088]
In one embodiment of the invention, the plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. When the synchronization detection information indicates that the (N+1) th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0089]
In one embodiment of the invention, when the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, the erasure locator information generation section determines at least one symbol provided between the consecutive synchronization data pieces as representing erasure. [0090]
According to still another aspect of the invention, a reproduction apparatus for reproducing a composite coded data piece from a recording medium having the composite coded data piece recorded thereon is provided. The composite coded data piece includes a first coded data piece which is error-correction-coded using a first error correction code, a second coded data piece which is error-correction-coded using a second error correction code having a lower degree of redundancy than that of the first error correction code, and a plurality of synchronization data pieces. The first coded data piece includes a plurality of first symbols. The second coded data piece includes a plurality of second symbols. At least one first symbol is provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one of the plurality of second symbols is provided at least between a synchronization data piece and a first symbol. The reproduction apparatus includes a reading section for reading the composite coded data piece from the recording medium and outputting the first coded data piece, the second coded data piece, and the plurality of synchronization data pieces; a synchronization detection information generation section for detecting states of the plurality of synchronization data pieces and generating synchronization detection information which represents the detection result; an error location information generation section for performing error correction of the first coded data piece and generating error location information which represents an error location of the first coded data; an erasure locator information generation section for generating at least first erasure locator information and second erasure locator information which represent an erasure position of the second coded data piece, based on the error location information and the synchronization detection information; and an erasure error correction section for performing erasure error correction of the second coded data piece based on at least one of the first erasure locator information and the second erasure locator information. When there is an error which cannot be corrected based on the first erasure locator information, the erasure error correction section performs erasure error correction of the second coded data piece based on the second erasure locator information. [0091]
In one embodiment of the invention, when all the errors can be corrected based on the first erasure locator information, the erasure locator information generation section generates erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the first erasure locator information. When all the errors can be corrected based on the second erasure locator information, the erasure locator information generation section generates erasure locator information for erasure error correction of another second coded data piece using an identical method as the method used for generating the second erasure locator information. [0092]
In one embodiment of the invention, when the synchronization detection information indicates that there is a synchronization data piece which is not detected and the error location information indicates that no error is detected in the first symbols immediately on both sides of the undetected synchronization data piece, the erasure locator information generation section determines at least one of the plurality of second symbols provided adjacent to the undetected synchronization data piece as representing erasure. [0093]
In one embodiment of the invention, at least two first symbols are provided between two adjacent synchronization data pieces among the plurality of synchronization data pieces. At least one second symbol is provided between two adjacent first symbols among the at least two first symbols. When the error location information indicates that there is a first symbol detected to have an error and at least one of the error location information and the synchronization detection information indicates that one of a detected synchronization data piece and a first symbol detected to have no error is immediately on each of both sides of the first symbol detected to have an error, the erasure locator information generation section determines at least one of the plurality of second symbols provided adjacent to the first symbol detected to have an error as representing erasure. [0094]
In one embodiment of the invention, the plurality of synchronization data pieces include an Nth synchronization data piece and an (N+1)th synchronization data piece, where N is an integer. When the synchronization detection information indicates that the (N+1) th synchronization data piece is detected with a positional offset, the erasure locator information generation section determines at least one second symbol provided between the Nth synchronization data piece and the (N+1)th synchronization data piece as representing erasure. [0095]
In one embodiment of the invention, when the synchronization detection information indicates that any two or more data pieces from undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, the erasure locator information generation section determines at least one second symbol provided between the consecutive synchronization data pieces as representing erasure. [0096]
An error correction method and a reproduction apparatus according to the present invention function as follows. When a first symbol included in a first coded data piece having a relatively high degree of redundancy is detected to have an error or when no synchronization data piece is detected, the second symbols which are provided in the vicinity of such a first symbol or the undetected synchronization data piece have a high probability of incorrect and thus are determined to represent erasure. When a synchronization data piece is detected with a positional offset, symbols included in the coded data pieces located before such a synchronization data piece have a high probability of being incorrect and thus is determined to represent erasure. Symbols included in the coded data pieces located after such a synchronization data piece have a high probability of being correct and thus is determined not to represent erasure. When at least two of the undetected synchronization data pieces and synchronization data pieces detected with a positional offset are consecutive, data pieces which are read before the next correctly detected synchronization data piece have a high probability of being incorrect. Thus, symbols included in all the coded data pieces between those consecutive synchronization data pieces are determined to represent erasure. Owing to these methods, erasure positions can be determined with higher precision, and thus the error correction capability can be improved. [0097]
An error correction method and a reproduction apparatus according to the present invention are useful for, for example, error correction of composite coded data. [0098]
Thus, the invention described herein makes possible the advantages of providing an error correction method which is effective for generating erasure locator information using a result of error correction of a first coded data piece or a result of detection of a synchronization data piece and for performing erasure error correction of a second coded data piece using the erasure locator information, and a reproduction apparatus for carrying out such an error correction method. [0099]
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.[0100]